In a small bowl, combine the chili powder, kosher salt, paprika, smoked paprika, garlic powder, onion powder, cayenne pepper, black pepper, and cumin. Divide the mixture in half and reserve half for later use.
Cut the Boston butt into 6 even pieces and place into a 6- to 8-quart saucepan. Add half of the spice mixture and enough water to completely cover the meat, 3 to 3 1/2 quarts. Set over high heat, cover, and bring to a boil. Once boiling, reduce the heat to low and simmer until the meat is very tender and falling apart, 2 to 2 1/2 hours. Remove the meat from the pot to a cutting board, leaving the cooking liquid in the pot. Both meat and liquid need to cool slightly before making dough and handling. Remove any large pieces of fat and shred the meat into small pieces, pulling apart with your hands or using 2 forks.
Place a 4-quart saucepan over medium heat and add the vegetable oil. Once shimmering, add the onion and cook, stirring occasionally, until semi-translucent, approximately 3 minutes. Add the garlic, jalapeno, and remaining half of the spice mixture and continue to cook for another minute. Add the meat and cook until heated through, 2 to 3 minutes. Remove from the heat.
While the meat is cooking, place the husks in a large bowl or container and submerge completely in hot water. Soak the husks until they are soft and pliable, at least 45 minutes or up to 2 hours.
Make the dough: Place the cornmeal, salt, and baking powder into a large mixing bowl and stir to combine. Add the lard and, using your hands, knead together until the lard is well incorporated into the dry mixture. Gradually add enough of the reserved cooking liquid, 3 to 4 cups, to create a dough that is like thick mashed potatoes. The dough should be moist but not wet. Cover the bowl with a damp towel and set aside until ready to use.
Assemble the tamales: Remove the corn husks from the water and pat dry to remove excess water. Working in batches of 6, lay the husks on a towel and spread about 2 tablespoons of the dough in an even layer across the wide end of the husk to within 1/2 inch of the edges. Spoon about 1 tablespoon of the meat mixture in a line down the center of the dough. Roll the husk so the dough surrounds the meat, then fold the bottom under to finish creating the tamale. Repeat until all husks, dough, and filling are used. Tie the tamales around the center, individually or in groups of 3, with kitchen twine.
Cook the tamales: Stand the tamales upright on their folded ends, tightly packed together, in the same saucepan used to cook the meat. Add the reserved broth from making the dough and additional water, if needed, so the liquid comes to 1 inch below the tops of the tamales. Try not to pour the broth directly into the tops of the tamales. Cover the pan, place over high heat, and bring to a boil, approximately 12 minutes. Remove the lid, reduce the heat to low to maintain a low simmer, and cook until the dough is firm and pulls away easily from the husk, 1 to 1 1/2 hours.
Serve the tamales warm. For a "wet" hot tamale, serve with additional simmering liquid. Store leftover tamales, tightly wrapped in plastic wrap, in the freezer for up to a month. To reheat, remove the plastic wrap and steam until heated through.